Baphomet
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Peracetic Acid Preparation
Last night I tried to make peracetic acid by reacting 0.43 moles (67g) of Sodium Percarbonate and 3 moles Acetic Acid (730mL of 25% solution). This
allows the required 1:7 ratio to neutralise all the Sodium Carbonate and react to form the peroxyacid.
| Code: | 4 H3CCOOH + 2 Na2CO3 · 3 H2O2 > 4 Na.H3CCOO + H2O + 3 H2O2
3 H3CCOOH + 3 H2O2 > 3 H3CCOOOH + 3 H2O |
Now, Sulphuric Acid is usually employed as a catalyst but in this case would react with Sodium Acetate. Should I add a stoichiometric amount of H2SO4
(80ml), and then a little extra as catalyst?
Note the highest conc. of Acetic Acid available to me is 25%. My calculations show that the above prep can yield a peroxyacid conc. of up to 12%.
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kclo4
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You could do that but I think you may want to make it so it forms Sodium Bisulfate instead of Sodium Sulfate. I don't know if Sodium Bisulfate would
work as a catalyst, so perhaps it is best to play it safe and add an excess of H2SO4 for the bisulfate reaction.
This reaction would likely happen:
| Code: | Na2SO4 + HCOOCH3 = NaHSO4 + NaCOOCH3 |
I have heard that in solution NaHSO4 act as if it were a solution of Na2SO4 and H2SO4 - so perhaps this is unnecessary. Just something that might be
worth considering.
Why not use the 3% Hydrogen peroxide it will make it more dilute, but you won't have all those salts in there. If you only need a small amount you
could even concentrate the 3% by freezing it out. That gets a concentration of Hydrogen peroxide high enough to bleach your skin, and gums completely
white if you do not notice it is one you.
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Baphomet
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Thanks kclo4. Do you know if it is normal for the reaction mix to still be generating bubbles after 24 hours? I'm concerned that the H2O2 will offgas
too quickly resulting in low yields.
I've added the H2SO4. A lot of heat was generated naturally, some of the Acetic Acid boiled off. There was also a smell similar to chlorine which was
curious, perhaps Acetic Acid vapour can smell like that?
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Klute
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I'm very sceptical that you will get 12% peracetic from 25% AcOH. Could you please details your calculations?
Can you get sodium perborate? This is a much more usefull alternative that percarbonate IMHO.
Now the problem you will have is to selectivily titrate peracetic, excluding free H2O2 or persalts, but honestly there is much too much water around
to get even close to 10% peracetic IMHO.
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Ebao-lu
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If you have water in the system, you'll get an equilibrium mix.
CH3COOH + H2O2 <-(H2SO4)-> CH3COOOH + H2O
I dont know the equilibrium ratio, but once came accross some comercially sold peracetic acid, that was an equilibrium mix apparently. It had a
significant amount of H2O2 and acetic acid, as it was written in the content. So the equilibrium ratio is somewhat close to 1, i suppose.
All manipulations with adding H2SO4 to sodium acetate solution to get NaHSO4(or Na2SO4), adding extra acid, will bring water to the system (at least,
if H2SO4 is dilute) and the concentration of PAA will decrease.
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Baphomet
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| Quote: | Originally posted by Klute
I'm very sceptical that you will get 12% peracetic from 25% AcOH. Could you please details your calculations?
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312mL of the acetic solution is to neutralise the sodium carbonate, the other 418mL theoretically should equilibrialise with H2O2 to form the peracid.
While the traditional preps call for GAA and 30% H2O2, I'm trying the opposite using a concentrated form of H2O2 and a weaker acetic acid.
| Quote: |
Can you get sodium perborate? This is a much more usefull alternative that percarbonate IMHO.
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I wish! 
| Quote: |
Now the problem you will have is to selectivily titrate peracetic, excluding free H2O2 or persalts, but honestly there is much too much water around
to get even close to 10% peracetic IMHO. |
Persalts would not be a problem would they? Since H2SO4 is a stronger acid than PAA, so it's salts should form preferably.
But I'm interested in knowing why you think it won't work. I have a detailed calc in a spreadsheet that will be uploaded tonight.
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Baphomet
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Ebao-lu, does this mean that PAA is only ever in equilibrium with acetic acid and H2O2? Maybe this is what you are referring to Klute?
So if I want 12% PAA I need a stronger solution..
The good news is that my H2SO4 is 100% so I can adjust the strength that way 
As long as Persalts do not chew up the Acetic Acid
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kclo4
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If you can't get over this problem of getting a nice solution of peracetic acid, perhaps you could look into a hydroponic store. I believe they often
sell Hydrogen peroxide around the concentration of 30%
Also look into a chemical called Oxone, also known as Potassium peroxymonosulfate. It can be turned into hydrogen peroxide IIRC and also has its very
own uses as an oxidizer. I believe it is sold as a pool chemical in the popular stores.
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Klute
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Indeed peracetic acid is always in equilibrium with acetic and H2O2, evene when using 30% H2O2 and glacial AcOH you only get something like 20-30%
peracetic.
For the titration, apparently there is a simple way of doing this:
Determination of peracetic acid and hydrogen peroxide in a preparation
Bodiroga M, Ognjanović J.
Vojnosanit Pregl.;59(3), 277-9 (2002)
Abstract:
Iodometric and permanganometric titrations were used for determination of peracetic acid and hydrogen peroxide (H2O2) in the mixture. Two
procedures were described and compared. Titrations could be done in only one vessel, in the same reaction mixture, when iodometric titration of
peracetic acid was continued after the permanganometric titration of H2O2, (procedure A). Peracetic acid and H2O2, as oxidizing agents, reacted with
potassium iodide in an acid medium, evolving iodine. This reaction was used for the quantitative iodometric determination of total peroxide in
procedure B. H2O2 reacted with potassium permanganate in acid medium, but peracetic acid did not react under the same conditions. That made possible
the selective permanganometric determination of H2O2 in the presence of peracetic acid. The procedure B was performed in two titration vessels (KV =
3.4% for peracetic acid, 0.6% for H2O2). The procedure A for iodometric determination of peracetic acid in one titration vessel after permanganometric
titration of H2O2 was recommended (KV = 2.5% for peracetic acid, 0.45% for H2O2).
And I highly recommend reading the following article, all the calculations you need:
Preparation of peracetic acid from acetic acid and hydrogen peroxide: experimentation and modeling
Chinese Journal of Process Engineering; (1)8, 35-41 (2008)
Link
[Edited on 27-2-2009 by Klute]
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Ebao-lu
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| Quote: | | The good news is that my H2SO4 is 100% so I can adjust the strength that way |
Then you can distill off the high concentrated AcOH form AcONa + H2SO4. Also, do you have there
CO(NH2)2*H2O2 avaliable? It could be sold either for desinfr
ection in pharmacies, or as a bleach sometimes. The product would be craped with urea then, but AFAIK urea forms a low soluble CO(NH2)2*CH3COOH adduct
with acetic acid if cooled(so maybe you can remove extra acetic acid as well). But be careful if you plan to get high concentrated PAA - it becomes
sensetive at high concentrations. For most organic reactions, dilute solutions of PAA would do.
[Edited on 27-2-2009 by Ebao-lu]
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aliced25
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Quote: Originally posted by Baphomet  | Last night I tried to make peracetic acid by reacting 0.43 moles (67g) of Sodium Percarbonate and 3 moles Acetic Acid (730mL of 25% solution). This
allows the required 1:7 ratio to neutralise all the Sodium Carbonate and react to form the peroxyacid.
| Code: | 4 H3CCOOH + 2 Na2CO3 · 3 H2O2 > 4 Na.H3CCOO + H2O + 3 H2O2
3 H3CCOOH + 3 H2O2 > 3 H3CCOOOH + 3 H2O |
Now, Sulphuric Acid is usually employed as a catalyst but in this case would react with Sodium Acetate. Should I add a stoichiometric amount of H2SO4
(80ml), and then a little extra as catalyst?
Note the highest conc. of Acetic Acid available to me is 25%. My calculations show that the above prep can yield a peroxyacid conc. of up to 12%.
|
Just found some interesting papers that suggest that percarbonate in acetic acid gives H2O2 and carbon dioxide - ie. percarbonate is a dry source of
H2O2 (a carrier), but will not react to form peracetate. The papers go on to describe perborate as a peracid, but one that when mixed with acetic acid
and AGED produces peracetic acid... Perborate is produced by reacting H2O2 and boric acid.
Ok, so (a) percarbonate reacts with acetic acid to give H2O2 and carbon dioxide; (b) boric acid reacts with H2O2 to give perborate; (c) perborate
(and presumably H2O2 in the presence thereof) react with acetic acid to give peracetic acid.
So boric acid is effectively acting the same way as H2SO4, catalyzing the reaction between H2O2 and acetic acid. Anyone else think that percarbonate +
acetic acid + boric acid + time would give a solution of perborate + peracetatate in acetic acid? With no additional water?
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Dr.Bob
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| Quote: Originally posted by Ebao-lu |
Then you can distill off the high concentrated AcOH form AcONa + H2SO4.
But be careful if you plan to get high concentrated PAA - it becomes sensitive at high concentrations. For most organic reactions, dilute solutions
of PAA would do. |
Be very careful when distilling anything with peracids in it. I have seen the results of two peracid reactions going bad over the years, and both
made significant explosions, one injuring a person on the outside of a safety glass hood. In many cases the solvent is removed until the organics and
peroxides are left concentrated, and they simple react. So using a lower concentration gives a much better margin off error, especially if you are
not experienced in that area. I would be very cautious with those reactions, even now.
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chemrox
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http://www.jproeng.com/qikan/manage/wenzhang/207239.pdf
Has anyone else tried loading this? I couldn't open it from my laptop. Might be an MSN issue. My laptop has Win 7 Pro on it ;^(
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Waffles SS
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Someone has experience on making Peracetic acid solution in Ethyl acetate?
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Dr.Bob
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I would be extremely careful trying to handle peracids in organic solvents. Some of those systems are stable, but many can explode violently,
especially if there are other impurities. I saw the results of that once.
Also, distilling peracids can be very bad, much better to distill/concentrate the acetic acid or H2O2 before mixing with other chemicals, then your
peracid will be much stronger to begin with. But I am only familiar with doing the GAA and H2O2 method, which, as stated, is in equilibrium. Also,
apparently making the peracetic acid from acetic anhydride and H2O2 allows for much higher peracid equilibrium, which makes perfect sense.
From wikipedia: Concentrated peroxyacetic acid, an organic peroxide, explodes at 110 °C. That is for pure material-not in contact with
organics-for those situations, the decomp. temp is much lower.
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Waffles SS
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Thanks Dr.Bob
I think adding Ac2O to mixture of Acetic acid + Ethyl acetate and H2O2 push equilibrium to right and help to make Peracetic acid solution in Ethyl
acetate
AcOH + H2O2 = AcOOH + H2O
I decide to Methylation-Hydroxylation some unsaturated compounds accoding to US3806548.(it mentioned solution of Peracetic acid in Ethyl acetate
needed)
[Edited on 31-7-2014 by Waffles SS]
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Praxichys
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| Quote: Originally posted by Dr.Bob | I would be extremely careful trying to handle peracids in organic solvents.
[snip]
From wikipedia: Concentrated peroxyacetic acid, an organic peroxide, explodes at 110 °C. That is for pure material-not in contact with
organics-for those situations, the decomp. temp is much lower. |
Using the glacial acetic acid route sans water, be careful about diacetyl peroxide, another dangerously unstable organic peroxide.
| Quote: | | Diacetyl peroxide can be formed when a mixture of hydrogen peroxide, and excess acetic anhydride reacts with one of the
reaction products peracetic acid. |
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